The maintenance of a constant internal environment in an organism is termed:

plant because they survive by water, sunlight, ex.

explanation:

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".